Unsaved people ....
...some of which would be 'lost sheep'...
The warnings CANNOT apply to our relationships with the unsaved. We have the Gospel message for them.
The warnings apply to evil people within the congregation who are abusing their position, teaching error, leading followers after themselves, etc.
Hebrews describes their ilk -
6:4 It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, 5 who have tasted the goodness of the word of God and the powers of the coming age 6 and who have fallenaway, to be brought back to repentance. To their loss they are crucifying the Son of God all over again and subjecting him to public disgrace. 7 Land that drinks in the rain often falling on it and that produces a crop useful to those for whom it is farmed receives the blessing of God. 8 But land that produces thorns and thistles is worthless and is in danger of being cursed. In the end it will be burned.
10:26 If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, 27 but only a fearful expectation of judgment and of raging fire that will consume the enemies of God. 28 Anyone who rejected the law of Moses died without mercy on the testimony of two or three witnesses. 29 How much more severely do you think someone deserves to be punished who has trampled the Son of God underfoot, who has treated as an unholy thing the blood of the covenant that sanctified them, and who has insulted the Spirit of grace? 30 For we know him who said, ‘It is mine to avenge; I will repay,’ and again, ‘The Lord will judge his people.’ 31 It is a dreadful thing to fall into the hands of the living God.
12:15 See to it that no one falls short of the grace of God and that no bitter root grows up to cause trouble and defile many. 16 See that no one is sexually immoral, or is godless like Esau, who for a single meal sold his inheritance rights as the oldest son. 17 Afterwards, as you know, when he wanted to inherit this blessing, he was rejected. Even though he sought the blessing with tears, he could not change what he had done.
Specific examples would be the Pharisees who heard & saw Jesus & the signs he gave, & heard his warnings, yet rejected him, & the Apostolic Gospel. Later on some did apparently believe but sought to cause division - Acts 15 -
5 Then some of the believers who belonged to the party of the Pharisees stood up and said, ‘The Gentiles must be circumcised and required to keep the law of Moses.’
John warns of such -
2 John 7 I say this because many deceivers, who do not acknowledge Jesus Christ as coming in the flesh, have gone out into the world. Any such person is the deceiver and the antichrist. 8 Watch out that you do not lose what we have worked for, but that you may be rewarded fully. 9 Anyone who runs ahead and does not continue in the teaching of Christ does not have God; whoever continues in the teaching has both the Father and the Son. 10 If anyone comes to you and does not bring this teaching, do not take them into your house or welcome them. 11 Anyone who welcomes them shares in their wicked work.
3 John 9 I wrote to the church, but Diotrephes, who loves to be first, will not welcome us. 10 So when I come, I will call attention to what he is doing, spreading malicious nonsense about us. Not satisfied with that, he even refuses to welcome other believers. He also stops those who want to do so and puts them out of the church.
See also the 7 letters of Revelation.
